Pet Talk - Pet Health
by Dr. Fran Good, DVM
November 24, 2003
It's a smart question, because Toxo is excreted in the feces, but the short answer to the smart question is that human infections by Toxo are usually asymptomatic. The only people who need to watch out for Toxo are pregnant women, because Toxo can be transmitted transplacentally to the embryo. If the infection occurs in the first trimester, fetal death and/or abortion occurs. If the transmission occurs in the last trimester, then neurological and visual abnormalities are the most common result.
There are two ways to come
in contact with Toxo. The first is eating the undercooked meat
of something else that's been infected with Toxo - and almost
anything vertebrate can be infected - or by eating the Toxo life
stage called the sporulated oocyst. Since oocysts are formed
in cat intestines, and excreted in cat poop, those in contact
with cats are at greatest risk of contracting the disease.
This doesn't solve the entire problem, but it minimizes it. The unfortunate part is that oocysts can survive in the environment up to a year, and there's no guarantee that they're all ending up in the cat box. The recommendation is that pregnant women avoid contact with cats as much as they can. Most experts agree that women who get infected before they get pregnant are not at risk for transplacental transmission.
Finally, the answer to the question of the otter deaths, and risk from freshwater runoff is - I dunno. Like I said earlier, it takes a certain set of conditions for oocytes to sporulate, and what those conditions are, you'd have to ask a bacteriologist. Since otters are dying of Toxo, there must be some risk to them. But to humans? Only to pregnant women, as the rest of us tend toward asymptomatic infections, and only if the conditions are right for sporulation of the oocysts.
To put it in perspective a little, the cycle that produces oocysts is self-limiting. A test of a humane society showed that 50% of all the cats had been infected with Toxo, but only 1% of the cats were shedding oocysts. It's not all cats all the time, just infected cats for a small period of time.
There are plenty of other things,
much more dangerous, and more likely to affect you, that would
make better candidates for causing insomnia. I guess I wouldn't
lose any sleep over this one.
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